Amorphous Silicon Research Articles

The advantages of employing i-a-SiOX:H as a buffer layer in hydrogenated amorphous silicon oxide solar cells

Abstract This study focuses on a p-i-n single junction solar cell made of hydrogenated amorphous silicon oxide (a-SiOx:H), aiming to enhance solar cell efficiency by mitigating the impact of discontinuities and mismatches occurring at the i/p defect-rich interface between the window layer and the absorber layer. To address this concern, the impact of adding a thin i-a-SiOx:H buffer layer between the p-a-SiOx:H window layer and the i-a-SiOx:H active layer was investigated through numerical modeling using the AMPS-1D (Analysis of Micro-electronic and Photonic Structures) computer program. Implementing these changes led to a remarkable increase in conversion efficiency, rising from 5.714% to an impressive 8.929%. The increase in short-circuit current (JSC), however, is due to improved quantum efficiency at short wavelengths between 350 and 550 nm. Furthermore, enhancing the built-in potential (Vbi) at the i/p interface, combined with the buffer layer’s appropriate band gap energy, increases VOC (open-circuit voltage) from 850 to 993 mV. The substantial improvement in the fill factor (FF) from 63.1 to 83.1% can be largely attributed to the smoothed band offset, primarily facilitated by the presence of the buffer layer at the p/i interface, which led to more efficient extraction of photogenerated holes. To ensure effective usage of the buffer layer, the thickness of a-SiOx:H (buffer layer) varied between 3 nm and 9 nm, while the p-type doping concentration of the same layer was adjusted between 0 and 1020 cm−3. In summary, adding a 3 nm thick a-SiOx:H buffer layer with an intermediate band gap and with a p-type doping concentration (NA) below 1018 cm−3 at the i/p interface improves the electrical and optical properties of the p-i-n solar cells (EFF = 8.951%; VOC = 0.994 V; FF = 83.1%; JSC = 10.842 mA.cm−2).

First-principles study on the lithiation process of amorphous SiO anode for Li-ion batteries with Bayesian optimization.

Amorphous silicon monoxide (a-SiO), which contains Si atoms with various valence states, has attracted much attention as a high-performance anode material for lithium (Li) ion batteries (LIBs). Although current experiments have provided some information during charge/discharge cycles, further investigation of structural changes at the atomic scale is needed. To investigate the lithiation process of a-SiO using first-principles simulations and machine learning techniques, we developed a computational code employing Bayesian optimization to efficiently identify stable sites for Li insertion in the large search-space of amorphous models to reproduce the actual lithiation process and compared this approach to the conventional random scheme by applying it to an a-SiO model previously generated with neural network potentials. The lithiation process based on Bayesian optimization resulted in lower formation energies compared to the conventional random scheme, indicating a more stable structure. During lithiation, Li atoms tended to enter the silicon (Si) phase after the SiO2 phase, in agreement with experimental results. We analyzed the structural changes and observed significant differences in the structural evolution between the conventional and new schemes. Our study highlights the significant influence of the lithiation process on the structural transformation of a-SiO materials, which in turn affects the reversible capacity of the material. These findings will provide a framework for improving the performance and lifetime of a-SiO materials.

Magnetic Order in Nanogranular Iron Germanium (Fe0.53Ge0.47) Films.

We study the effect of strain on the magnetic properties and magnetization configurations in nanogranular FexGe1-x films (x = 0.53 ±0.05) with and without B20 FeGe nanocrystals surrounded by an amorphous structure. Relaxed films on amorphous silicon nitride membranes reveal a disordered skyrmion phase while films near and on top of a rigid substrate favor ferromagnetism and an anisotropic hybridization of Fe d levels and spin-polarized Ge sp band states. The weakly coupled topological states emerge at room temperature and become more abundant at cryogenic temperatures without showing indications of pinning at defects or confinement to individual grains. These results demonstrate the possibility to control magnetic exchange and topological magnetism by strain and inform magnetoelasticity-mediated voltage control of topological phases in amorphous quantum materials.

The effect of the composition of hepatoprotective action on biochemical and morphostructural changes in the body of laying hens under thermal stress

To reduce the negative effects of hyperthermia on the body of farm animals and poultry, various drugs and feed additives are currently used. Which do not have sufficiently adaptogenic and antitoxic properties. We studied the effect of a hepatoprotective composition consisting of dried live yeast, amorphous silicon dioxide, propylene glycol, calcium propionate, ascorbic acid, manganese, copper and zinc chelates, methionine and choline chloride on the variability of biochemical and morphological parameters of the body of laying hens under temperature stress. It was simulated by increasing the air temperature in a building where laying hens were kept from 18.0 ± 1.0 °C to 28.0 ± 1.0 °C for 48 hours. Due to hyperthermia, changes in biochemical and morphofunctional parameters were observed in the tissues and organs of birds. The obtained values of the biochemical parameters of blood serum in the birds of the control group indicated the intensity of the adaptive capabilities of their body. A complex of morphological changes confirmed a violation of protein metabolism and the regenerative-compensatory process. Pathological changes in the structure of the duodenum, characteristic of catarrhal-necrotic duodenitis, were identified. The stress reaction was also reflected in the condition of the heart muscle, in which an inflammatory process developed against the background of granular dystrophy of cardiomyocytes. The results of biochemical studies of blood serum in birds of the experimental group indicated an increase in the anti-stress response to a temperature stimulus under the influence of the studied composition (tendency to increase glucose and calcium, increase alkaline phosphatase activity by 47.4 %). The introduction of a hepatoprotective composition into the diet of laying hens during periods of temperature stress did not lead to disruption of the structure of tissues and organs, preserving cellular metabolic mechanisms. The

Improving the photoswitching performance of a transistor with amorphous metal oxide semiconductor thin film by a gradient annealing approach

Metal oxides are attracting attention as electronic mate rials in research and industry. Thin films of amorphous indium gallium zinc oxide (a-IGZO) exhibit low absorbance in the visible spectrum, making them ideal components in transparent electronics. To widen the scope of use for thin film transistor (TFT) devices based on a-IGZO in on-chip sensing applications, photoresponsive behavior has been achieved by proper engineering of the active layers by either introducing a photosensitive top layer or using a method to generate localized states inside the band gap. In this paper, we propose a bilayer structured with the use of thermal annealing of a-IGZO film at different temperatures. Thermal annealing has been shown to improve the electrical performance of the TFT devices because of the improved film quality but negatively affects the photoresponsivity by removing tarp sites that play an important role in both charge generation and photomultiplication via the photogating effect. Therefore, here we propose an a-IGZO film with a high temperature-annealed bottom layer and pristine top layer. The bottom layer plays a vital role in the charge transport behavior, resulting in a low threshold voltage and subthreshold swing similar to the device with a fully annealed film, while the photoresponse of the device is driven by the higher density of gap states in the pristine top layer. This proposed method is advantageous to previously published procedures due to the simplicity of using no additional materials and complex steps to introduce trap sites into the photoactive layer, but only differential annealing temperature.

A Comprehensive Guide to Fully Inkjet‐Printed IGZO Transistors

AbstractIn this concise review, the recent advancements in fully inkjet‐printed (IJP) indium‐gallium‐zinc‐oxide (IGZO) thin‐film transistors (TFTs) over the past years are discussed. IGZO has replaced hydrogenated amorphous silicon (a‐Si:H) as the primary channel material for liquid‐crystal display TFTs and has gained further attention due to the solution processability of IGZO inks. Despite the longstanding practice of printing IGZO for approximately fifteen years, the realization of fully inkjet‐printed devices, including both dielectric and electrode components, represents a recent milestone in research, potentially heralding a cost‐effective era for IGZO transistors. In this review, following an introductory exposition of IGZO, the focus is on the different ink formulations, currently deployed for solution‐processed IGZO devices, the intricacies of the printing procedure involved are delineated, and ongoing research endeavors pertaining to the printing of dielectrics and electrodes for such devices are expounded upon.

Enhancing performance of microbolometers by utilizing low-temperature polycrystalline silicon

In response to the urgent need for advanced noncontact temperature sensing technologies to mitigate pandemic transmission, there has been a notable surge in global demand. Thermal cameras, combined with infrared sensors, are critical not only for high-resolution imaging but also for cost-effective commercialization. Amorphous silicon-based microbolometers offer advantages in terms of integration and cost compatibility with conventional silicon processes. However, they suffer from limitations in their electrical properties, particularly in the noise-equivalent temperature difference. This study examines the effectiveness of low-temperature polycrystalline silicon (poly-Si) as an active material for microbolometer cells compared to amorphous silicon, focusing on improving the temperature coefficient of resistance (TCR) and lowering the noise density. Our investigation reveals that various parameters, such as dehydrogenation temperatures ranging from 350 to 550 °C, diverse laser annealing techniques (including single, step and multishot methods), and laser power density levels ranging from 150 to 300 mJ/cm2, influence the grain size trends of poly-Si. Using these methods, we produced poly-Si films with grain sizes ranging from 15 to 40 nm, which were used as the active layer in bolometer cells. The final part of our study assessed the TCR and noise density in devices with different poly-Si grain sizes. The TCR/noise density ratio was 3.5 times better in poly-Si devices compared to amorphous silicon devices. This study evaluates poly-Si as an active material for microbolometers, paving the way for future research and development in next-generation infrared sensor technology.

Magnetron sputtered silicon thin films for solar cell applications

One of the important directions of research in photovoltaics is the development of new thin-film technology, which can replace the currently used, more expensive bulk silicon technology. The article discusses the findings from research focused on optimizing the parameters for the deposition of silicon thin films with P-type electrical conductivity for applications in photovoltaics. The growth rate was determined depending on the change in substrate temperature using reflectometry and the influence of deposition time on optical properties was determined using UV/VIS spectroscopy. Photovoltaic structures were made on substrates with an ITO layer and their electrical parameters were measured. The authors applied the magnetron sputtering method to deposit the layers, selecting it over the commercially used the chemical vapor deposition (CVD) method. This replacement could alleviate the necessity for high temperatures and broaden the potential applications of thin-film solar cells.

A Review of Wide Bandgap Semiconductors: Insights into SiC, IGZO, and Their Defect Characteristics.

Although the irreplaceable position of silicon (Si) semiconductor materials in the field of information has become a consensus, new materials continue to be sought to expand the application range of semiconductor devices. Among them, research on wide bandgap semiconductors has already achieved preliminary success, and the relevant achievements have been applied in the fields of energy conversion, display, and storage. However, similar to the history of Si, the immature material grown and device manufacturing processes at the current stage seriously hinder the popularization of wide bandgap semiconductor-based applications, and one of the crucial issues behind this is the defect problem. Here, we take amorphous indium gallium zinc oxide (a-IGZO) and 4H silicon carbide (4H-SiC) as two representatives to discuss physical/mechanical properties, electrical performance, and stability from the perspective of defects. Relevant experimental and theoretical works on defect formation, evolution, and annihilation are summarized, and the impacts on carrier transport behaviors are highlighted. State-of-the-art applications using the two materials are also briefly reviewed. This review aims to assist researchers in elucidating the complex impacts of defects on electrical behaviors of wide bandgap semiconductors, enabling them to make judgments on potential defect issues that may arise in their own processes. It aims to contribute to the effort of using various post-treatment methods to control defect behaviors and achieve the desired material and device performance.

Strong spherical V2O5/TiO2–SiO2 composites obtained by template combined with sol-gel method

This study is devoted to the preparation of strong spherical composites V2O5/TiO2–SiO2 by a combined template and sol-gel method. The composition, size and shape of the colloidal particles in butanol ash with tetrabutoxytitanium and tetraethoxysilane, as well as the physicochemical processes leading to the strengthening of the spherical agglomerates obtained using an anion exchanger with a gel structure, have been determined. Electrophoresis, small-angle X-ray scattering, and viscometry were used to demonstrate the presence in the sol of positively charged colloidal particles of lenticular and cylindrical shape, whose size, when the sol is stabilised, reaches 53 Å. The absorption of the sol by the anion exchanger in vanadium form is due to the equalisation of the osmotic pressure in the anion exchanger/sol system. Spherical composites with a diameter of 300 µm were obtained. It was shown by X-ray diffraction that the composites consist of V2O5 with an orthorhombic structure, TiO2 with an anatase structure, and amorphous silicon dioxide. The interaction at the interface between the phases of V2O5 with TiO2 and SiO2, which leads to the strengthening of the sphere of the V2O5/TiO2–SiO2 composite, has been demonstrated by IR and Raman spectroscopy. The results obtained can be used for the synthesis of MxOy/TiO2–SiO2 oxide composites with spherical agglomerates.

A study on the high mobility and improved reliability of pr-doped indium zinc oxide thin film transistors

Abstract It is generally accepted that there is a trade-off relationship between mobility and stability for oxide thin film transistor (TFT) devices. Different doping ratios of Ln praseodymium (Pr) into indium (In) zinc (Zn) oxide have been employed as the active layer to get 1# and 2# amorphous oxide semiconductor (AOS) TFTs in this work. The 1#-based TFTs exhibited a high mobility of 49.84 cm2 V−1 s−1 due to the increased concentration of In. By further elevating the Pr doping ratio and adjusting In/Zn ratio of the film, the 2#-based TFT obtained both a good mobility of 26.65 cm2 V−1 s−1, and a promising stability, showing a positive-bias temperature stress stability of ΔV TH = 1.56 V and a negative-bias temperature illumination stress stability of ΔV TH = −1.47 V. It was revealed that the low energy charge transfer state of Pr in 2# film absorbs the visible light, leading to suppressed photo-induced carriers and thus a good illumination reliability of the 2#-based TFTs. In practice, the LCD panel based 2# ACT TFT shows a well stable performance even under 10 000-nit illumination. The result indicates a promising strategy to accelerate the commercialization of AOS TFTs to large-panel display production.

Structural, electronic, and optical-absorption properties of 2D Si thin films

AbstractRecent experimental studies highlighted the potential of thin-film crystalline silicon (Si) for high-efficiency solar cells. Using density functional theory, we investigated 2D Si thin films across various orientations, thicknesses, and surface structures to elucidate their structure–property relationships. Through surface-energy calculations and Wulff construction, we determined the crystal habit of Si, which aligns with available experimental observations. Electronic-structure calculations underscored the critical role of valence saturation on surfaces in enabling semiconducting behavior in Si thin films, essential for optical applications. From optical-absorption calculations, we identified the surface index exhibiting the highest absorption coefficients for thin films Si solar cell applications. Graphical abstract

[formula omitted] Affects the crystalline calcium silicate hydrate minerals synthesized by fly ash-based silicon extraction solution and lime milk

When extracting amorphous silicon from fly ash using a strong alkaline solution, other elements such as Al also enter the silicon extraction solution in the form of AlOH4−. To systematically investigate the impact of AlOH4− on the synthesis of typical calcium silicate hydrate crystals in a silicon extraction solution, a specific amount of AlOH4− was added to the silicon extraction solution, and calcium silicate was hydrothermally synthesized at 90℃ and 230℃. Scanning electron microscopy (SEM) and Brunner−Emmet−Teller (BET) analysis revealed that with the increasing in AlOH4− content, microporous calcium silicate gradually loses its microporous morphology. While the specific surface area shows no significant change, the median pore diameter first increases from 1.47 nm to 1.58 nm and then decreases to 1.55 nm. The xonotlite fibers underwent a gradual refinement, diminishing from 0.28 to 0.15 µm. Simultaneously, the specific surface area increases from 28.87 to 56.8 m2/g. At an AlOH4− concentration of 3 mol/L, the microscopic morphology transforms into a sheet-like structure. X-ray diffraction (XRD) analysis reveals that AlOH4− promotes the formation of tobermorite while inhibiting the further development of calcium silicate. Additionally, Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance indicate that Al can replace Si in the calcium silicate hydrate system, primarily substituting positions the Q2 and Q3 sites. Qualitatively, it is suggested that with the increasing incorporation of Al, the polymerization degree of the silicon-oxygen tetrahedra decreases. According to experimental results, the concentration of AlOH4− should be below 0.05 mol/L when synthesizing microporous calcium silicate hydrate and less than 0.2 mol/L when synthesizing fibrous xonotlite-type calcium silicate hydrate.

Interfacial Reaction Boosts Thermal Conductance of Room‐Temperature Integrated Semiconductor Interfaces Stable up to 1100 °C

AbstractOverheating has emerged as a primary challenge constraining the reliability and performance of next‐generation high‐performance (ultra)wide bandgap (WBG or UWBG) electronics. Advanced heterogeneous bonding of high‐thermal‐conductivity WBG thin films and substrates not only constitutes a pivotal technique for fabricating these electronics but also offers potential solutions for thermal management. This study presents the integration of 3C‐silicon carbide (SiC) thin films and diamond substrates through a surface‐activated bonding technique. Notably, following annealing, the interfaces between 3C‐SiC and diamond demonstrate an enhancement in thermal boundary conductance (TBC), reaching up to ≈300%, surpassing all other grown and bonded heterointerfaces. This enhancement is attributed to interfacial reactions, specifically the transformation of amorphous silicon into SiC upon interaction with diamond, which is further corroborated by picosecond ultrasonics measurements. After annealing at 1100 °C, the achieved TBC (150 MW m−2 K−1) is among the highest among all bonded diamond interfaces. Additionally, the visualization of large‐area TBC, facilitated by femtosecond laser‐based time‐domain thermoreflectance measurements, shows the uniformity of the interfaces which are capable of withstanding temperatures as high as 1100 °C. The research marks a significant advancement in the realm of thermally conductive WBG/substrate bonding, which is promising for enhanced cooling of next‐generation electronics.

Multi-Color Spaceplates in the Visible.

The ultimate miniaturization of any optical system relies on the reduction or removal of free-space gaps between optical elements. Recently, nonlocal flat optic components named "spaceplates" were introduced to effectively compress space for light propagation. However, space compression over the visible spectrum remains beyond the reach of current spaceplate designs due to their inherently limited operating bandwidth and functional inefficiencies in the visible range. Here, we introduce "multi-color" spaceplates performing achromatic space compression at three distinct color channels across the visible spectrum to markedly miniaturize color imaging systems. In this approach, we first design monochromatic spaceplates with high compression factors and high transmission amplitudes at visible wavelengths based on a scalable structure and dielectric materials widely used in the fabrication of meta-optical components. We then show that the dispersion-engineered combination of monochromatic spaceplates with suitably designed transmission responses forms multicolor spaceplates that function achromatically. The proposed multicolor spaceplates, composed of amorphous titanium dioxide and silicon dioxide layers, efficiently replace free-space volumes with compression ratios as high as 4.6, beyond what would be achievable by a continuously broadband spaceplate made of the same materials. Our strategy for designing monochromatic and multicolor spaceplates, along with the presented theoretical and computational results, show that strong space-compression effects can be achieved in the visible range. Our findings may ultimately enable a new generation of ultrathin optical devices for various applications.

Thermal atomic layer deposition-processed InHfZnO thin film transistors with excellent stability

In recent years, the downscaling of transistors has sparked considerable interest in the advancement of amorphous oxide semiconductors, particularly indium-hafnium-zinc oxide (IHZO) has remarkable potential in applications such as high-resolution displays and 3D NAND. For the first time, we propose the fabrication of IHZO thin film transistors (TFTs) via thermal atomic layer deposition (TH-ALD). The preparation, electrical properties, and stability of IHZO TFTs are investigated. The performance of TFT deposited at 250 °C and annealed in N2 atmosphere at 300 °C exhibits a high field-effect mobility (μ) of 22.53 cm2/Vs, a high Ion/Ioff of ∼107, a low threshold voltage (Vth) of 0.15 V, and a minimum subthreshold swing (SS) of 0.24 V/decade. Furthermore, the threshold voltage shifts (ΔVth) in TFTs annealed in N2 and O2 are 0.31 and 0.16 V, respectively. These enhancements are attributed to the defects suppression and remaining ionized oxygen vacancies result in increased electron concentration in N2-annealed films. In comparison, O2 annealing causes a reduction in field effect mobility but concurrently enhances stability due to the direct passivation of defects, which leads to fewer oxygen vacancies. Additionally, Hf content can also impact the performance of TFT devices, even a small addition of Hf also results in the effective reduction of the carrier concentration. These findings provide valuable insights into the device mechanism of IHZO TFTs, presenting a novel avenue for comprehending and augmenting their overall performance.

Formation of n-type polycrystalline silicon with controlled doping concentration by flash lamp annealing of catalytic CVD amorphous silicon films

Formation of n-type polycrystalline silicon with controlled doping concentration by flash lamp annealing of catalytic CVD amorphous silicon films

Multifunctional Double Band Mesh Antenna with Solar Cell Integration for Communications Purposes

A dual band flexible antenna based on a circularly polarized modified meshed patch antenna design. This article focuses on some of the most pressing issues in small satellite applications. The antenna optimization and improvement of antenna performance, such as radiation efficiency. As is well known, circular polarization is immune to the Faraday rotation effect in the ionosphere and can thus prevent a 3-dB loss in geo-satellite communication. With the use of the software program Computer Simulation Technology (CST), the proposed circularly polarized modified meshed patch antenna has been created. Therefore, this article also presents a modified design of a circularly polarized meshed patch antenna to reduce the complexity of the antenna and decrease the size as much as it is capable. However, a meshed patch antenna can support a high communication data rate. The antenna architecture will theoretically be consistent with the installation of solar panels. The antenna utilizes a conductive copper as the core material and the substrate using flexible polyimide. The design antenna is very small, having an overall size of 30 * 30 mm when compared to other conventional non-transparent antenna operating at the same frequencies of 2.6, 3.5 GHz. The antenna that is proposed involves two meshed patch elements of same size but in various shapes. Finally, the proposed antenna is integrated into a solar cell by using the amorphous silicon thin film.

Unveiling Nanoscale Ordering in Amorphous Semiconducting Polymers Using Four-Dimensional Scanning Transmission Electron Microscopy.

We present four-dimensional (4D) scanning transmission electron microscopy (STEM) analysis to obtain a high level of detail regarding the nanoscale ordering within largely disordered organic semiconducting polymers. Understanding nanoscale molecular ordering in semiconducting polymers is crucial due to its connection to the materials' important properties. However, acquiring such information in a spatially localized manner has been limited by the lack of a nanoscale experimental probe, weak signal from ordering, and radiation damage to the sample. By collecting nanodiffraction patterns with a high dynamic range pixelated detector, we acquired statistically robust, high signal-to-noise ratio diffraction patterns from semiconducting organic materials, including poly(3-hexylthiophene-2,5-diyl) (P3HT), P3HT/[6,6]-phenyl C61 butyric acid methyl ester, and indacenodithiophene-co-benzothiadiazole (IDTBT), which largely have disordered structures. Real-space images of the ordered domains were reconstructed from the 4D-STEM data set for a variety of scattering vectors and in-plane angles to capture the different molecular stacking distances and their in-plane orientation. These were then analyzed to obtain the average size of the ordered domains within the sample. Such measurements were arranged in a two-dimensional (2D) histogram, which showed a direct relationship between the type and size of molecular ordering. Complementary analyses, such as intensity variance and angular correlation, were applied to obtain ordering and symmetry information. These analyses enabled us to directly characterize the alkyl and π-π stacking of P3HT, as well as the fullerene domains caused by donor segregation in the P3HT sample. Furthermore, the analysis also captured changes in the P3HT domains when the fullerenes are incorporated. Lastly, IDTBT showed a much lesser degree of ordering without much disinclination between the domains within the 2D histogram. The 4D-STEM analysis that we report here unveils new details of molecular ordering that can be used to optimize the properties of this important class of materials.

Effect of coated graphene on friction and wear properties of nickel-based self-lubricating coatings prepared by laser cladding

Graphene is an ideal material for improving the self-lubricating properties of coatings, but the high-energy laser beam can damage graphene during the laser cladding process. Therefore, in this paper, amorphous silicon dioxide (SiO2) is used to surface coat graphene particles to obtain silica-coated graphene with core-shell structure (G@SiO2). By adding niobium carbide (NbC) as the ceramic reinforcing phase and G@SiO2 nanoparticles as the solid lubricant in Ni60, a self-lubricating composite coating was prepared on the surface of 45 steel matrix by laser cladding technology. It is shown that G@SiO2 can promote the grain refinement of NbC in the coating. On the other hand, the addition of G@SiO2 promotes the generation of hard phase of chromium carbide, which together with NbC improves the hardness of the material. The maximum microhardness of the composite coating was 946 HV, which was 302.7% higher than that of the 45 steel base material. The lowest coefficient of friction value of the coated material was 0.25, and the lowest wear amount was 2.45 × 106 μm3. Compared with the composite coating without added G@SiO2, the coefficient of friction of the coated material with the addition of G@SiO2 was reduced by 50% and wear amount was reduced by 62%.